Since their conception, portable computers, as with all computers, have faced the issue of thermal management as a result of heat generated by the processor and other components that are densely packed in the computer. As is well known, many components of computers are sensitive to excessive heat that can degrade performance and result in damage.
The packaging of the portable computer has evolved into the use of a case in which, in a base portion, a keyboard is positioned adjacent to the user and on which on a hinged cover, including a display, is positioned facing the user when the cover is open. The package or case is about the size of a notebook, weighs about 5 pounds, and covers a typical size of about a 297 by 210 millimeter(mm) area.
Within the base, as a result of the capacity and performance increases, thermal management is often an important consideration in the computer design. In the last few years, the thermal dissipation requirements of portable computers have been rapidly increasing. For example, typical portable personal computers generate heat that must be dissipated in the range of from about 10 watts to 20 watts and beyond, in part a result of increasing central processing unit (CPU) performance and for a further part by additional function capabilities such as digital video disk (DVD), modem, audio and video that are being added.
Among the thermal management constraints encountered in design are the fact that the components of the computer are generally locallized heat generating elements that are enclosed in a physically small space in that base portion and are operated at close temperature tolerances. The base portion in turn usually rests in contact with the user so that high temperatures generated in the base are immediately apparent to the user. Passive cooling methods are most desirable because no power is consumed, no noise is generated and very little additional space is required. The best that can be done at the present state of the art, even including providing additional passive cooling capacity through the use of heat pipe technology, is from about 15 to about 20 watts. One way to increase cooling capacity is to add an active cooling device such as a fan. This has not been considered desirable because such devices take up space, consume power and generate noise. Space and battery power are at a very high premium in portable computers, and noise is highly undesirable.